1. Field of the Invention
The present invention relates to a differential assembly, and more particularly to a differential assembly having a number of teeth of side gears and a number of teeth of pinion mate gears optimized for improving gear power density and reducing size.
2. Description of the Prior Art
Conventionally, differential assemblies, well known in the prior art, are arranged in a power transmission system of a motor vehicle to allow a pair of output shafts operatively coupled to an input shaft to rotate at different speeds, thereby allowing the wheel associated with each output shaft to maintain traction with the road while the vehicle is turning. Such a device essentially distributes the torque provided by the input shaft between the output shafts. A conventional differential assembly comprises a rotatable differential case housing a pair of opposite side gears in meshing engagement with a set of pinion mate gears to permit differential rotation thereof.
Typically, a sum of a number of teeth of any one of differential side gears Z1 and a number of teeth of any one of pinion mate gears Z2 is more than nineteen. Usually differential assembly manufacturers employ the following combinations of the number of teeth of the differential side gear and the number of teeth of the pinion mate gear: 14×10, 16×10 or 13×9. Moreover, it is noticeable that a difference between the number of teeth of the side gears and the number of teeth of the pinion mate gears in each of the above combinations is greater than three, and the number of teeth of the side gears above each is greater than eleven.
At present, the differential side gears and the pinion mate gears are subject of contradictory requirements for increasing a gear strength and reducing their size due to ever increasing vehicle engine power and gear loads, and the necessity to reduce weight and size of the unsprung masses of the motor vehicles. The existing differential gears do not satisfy current requirements for gear tooth strength and the gear size.
Thus, there is a need for a combination of the differential side gear and the meshing pinion mate gear having optimized numbers of teeth providing improved power density and reduced size.